Performance of liqui-cel extra-flow membrane contractor in a pure water and in a0.2% sodium chloride solution (sno-str-2001-11)

摘要

After completion of SNO's first phase measurement of the neutrino charge current,two tons of salt were added into the SNO heavy water to increase the sensitivity of the neutral current measurement (Phase II). Liqui-Cel Extra-Flow Membrane Contactors (simply called Liqui-Cel) are used in the SNO heavy-water circulating system to remove the dissolved gases, such as oxygen, nitrogen, radon, and water vapor from the liquid water. One possible scenario with phase II operation is that the salt may leak through the Liqui-Cel membrane and come in contact with the vacuum pumps and other metal components of the Heavy-Water Vapor Recovery System. In this scenario, corrosion will damage these components, especially the vacuum pump (pfeiffer UniDry Pump with cast iron interior), and increase the operational difficulties. A series of tests for the behavior of the Liqui-Cel System in pure water and in salt systems was conducted at the Brookhaven National Laboratory in order to measure the transfer of (a) water vapor and (b) salt, if there is any, through the membrane. Initially, a 10-inch by 28-inch Liqui-Cel unit, identical to those used in the SNO heavy-water circulating system, was obtained from SNO site. However, extensive analysis showed that the membrane in this unit was defective; a replacement membrane would cost several thousand dollars. Instead, a smaller, 2.5-inch x 8-inch Liqui-Cel, obtained from Dr. Richard Helmers of the University of British Columbia, was used in this experiment. A comparison of the present experiment with the SNO heavy-water system is done with theoretical calculations. The results are discussed in the following sections.